Separation of compounds as objects of separation from raw materials as mentioned above is difficult or impossible by a customary distillation or crystallization method, so that special separation methods have been invented for and applied to respective raw materials.
The present inventors and the like had already discovered and patented methods according to which compounds as mentioned above can be highly selectively separated using either an aqueous solution of highly water-soluble substituted cyclodextrin such as branched cyclodextrin or an aqueous alkaline solution of unsubstituted cyclodextrin through formation of inclusion complexes and subsequent liquid-liquid extraction. An organic compound(s) as an object(s) of separation entrapped in an aqueous solution of a cyclodextrin is contacted with an organic solvent such as diethyl ether, or heated at a temperature of at least 60° C., whereby the compound(s) can be dissociated from the cyclodextrin and recovered. However, a continuous process of treatments ranging from entrapment of a compound(s) as an object(s) of separation in an aqueous solution of cyclodextrin to recovery thereof cannot easily be established. This is not limited to a case where a cyclodextrin is used as one kind of inclusion-complexing agent.
Accordingly, an object of this invention is to provide a continuous and selective method of entrapping a compound(s) as an object(s) of separation into an aqueous phase made of an aqueous solution of inclusion-complexing agent, and dissociating and recovering the entrapped compound(s) from the inclusion-complexing agent. Incidentally, the term “selective” used herein refers to a selectivity with which there can be attained an improvement in the purity of a compound as an object of separation, which is sufficient enough to provide a possibility of developing an industrially useful process.